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I have a 2100 sq ft, two story colonial built in 1800 in Mass. The oil furnace and blower push plenty of warm air thru the ductwork to both floors-- it heats up FAST.
Now I want to install central air, hoping it would be easy to add a coil above the furnace and set a 2 1/2 or 3 ton condenser on a pad 4 just feet from the basement furnace.
But more than one salesmen has told me I won't be able to cool the 2nd floor. I have NO returns on the 2nd floor, just the stairwell. I have two returns on the first floor.
After considering several costly options, including an attic AC unit, I'm wondering: can't I direct enough cool air to the 2nd floors by closing off first floor vents, or the use of a damper near the head of the ductwork? The next, least costly option would be to add one return from the 2nd floor, though it wouldn't be in the optimum location. First I'd try the system without it.
I've had a newer two story home before with a single central AC unit, so I know the 1st floor needs to be chilly to keep the 2nd floor comfortable -- but that house did have a 2nd floor return. Anybody with a historic home can understand why I'm trying to make the least invasive (and least expensive) plan work. I can only spend $4000-$6000.
I'm hoping to hear that one unit will be ok, even if not ideal. thanks
my grandparents live in a 100 year old historic plantation home, and although considerably larger than yours (approx 5000 sf) they have 2 units. especially if you dont have any returns upstairs, i just cant see it staying cool up there. heat rises, you know.
i guess too it depends on where you live, here in NC theres no way one unit with no upstairs returns could even remotely be considered comfy. or even bearable.
you may want to use window units upstairs if getting a dual system isn't in the budget. We gave my grandparents our old window units so he doesnt have to run the A/C up there as much. now he just uses the window units when someone is spending the night and will be up there (their bedroom is on first floor)
But more than one salesmen has told me I won't be able to cool the 2nd floor. I have NO returns on the 2nd floor, just the stairwell. I have two returns on the first floor.
That's also what I've been told, and it makes sense to me. Cool air sinks, so when the furnace kicks on the colder air from upstairs rushes toward the furnace and is replaced by the heat forced up through the ducts. Not so with AC, I've been told, because the fan just isn't powerful enough to suck in all that warm air from the second floor.
Sounds like for you an attic unit is the way to go.
Couldn't you just wring the neck of the people who put in the supply ducts but no returns? Argh. I don't have one connected return in my house; even though they're cut on the first floor, they just empty into the open basement.
Anyway, several contractors told me we could get by with one large return, run through a closet, that would require just one bump out on the first floor. Even that is too invasive for me -- my rooms are small. We're sticking with the window units for now, although I might investigate the high velocity, small-duct systems; seems they're kinda pricey, though.
We have central air in a home built in 2004 and in my experience it does not cool everything off evenly. The upstairs sometimes seems hotter, since heat rises. We also have a skylight which may contribute to this Not sure about that) But our central air unit is located outside behind the house
Really the problem is LESS TO Do with lack of returns and much more to do with the nature of older homes and poor insulation.
The "temperature delta" is going to be a HUGE factor in determining the feasibility of a single A/C unit cooling an older home -- when you have high outside temps / humidity the amount of cooling that possible with a standard forced air system that was sized for HEAT is probably inadequate to keep both floors comfortable.
There are MANY potential ways to deal with this and frankly two separate systems are among the MOST COSTLY and probably not needed for a house of this size. That said it is likely that DAMPERS WILL NOT do much to improve this situation as what happens is the BLOWER works harder pushing against the closed damper and any moisture can lead to HUGE headaches. Much better to try to use something like a high velocity system to use air flow to "flush out" the heat upstairs OR split system(s) where each room upstairs has individual air flow.
Of course UPGRADING INSULATION and AIR SEALING ought to be done BEFORE ANYTHING ELSE as the
root cause is that the air leaking in from your attic space is probably super heated by many degrees above the outside air. This heat literally soaks into the upstairs space and robs you of the cool air your A/C is supplying.
A qualified energy audit firm can detail where the air / heat is worst and validate that you have successfully sealed and insulated. In some cases these steps alone can eliminate the need to have complicated air handling schemes -- a single upstairs return (ideally in a HALLWAY OPEN TO THE STAIRS...) would pull enough uncooled air down to offset stratification of hot & cool air. The ductwork could be run in the back of closet or even through a main floor bathroom where a few inches could be spared and no major demolition would be needed.
In new construction the ease of running two separate sets of ducts for supply & return for each floor is probably smart -- the use of well timed set-back thermostats can especially result in significant energy savings. The hassles of retrofit would be very impractical unless gutting an older home!
You might consider the new "zone air conditioner" units. They are very quiet, don't ruin a window and work very well. They are also not so bad on electricity use as other choices.
I did have a big old 2 story colonial revival house in SW Missouri which a 3 ton unit cooled off pretty well. I don't remember if I had a return upstairs now that you mention it though.
Don't do the attic. It will be so noisy. My girlfriend has an attic airconditioner. You can hear it when it runs. It's terrible. And trust me, she's wealthy so it's top of the line. It's just not something you want above your sleeping areas. It's noisy enough during the day when we're upsetairs during my visits.
Don't do the attic. It will be so noisy. My girlfriend has an attic airconditioner. You can hear it when it runs. It's terrible. And trust me, she's wealthy so it's top of the line. It's just not something you want above your sleeping areas. It's noisy enough during the day when we're upsetairs during my visits.
I have been in high end homes where the A/C was in the attic and dead silent and others where you'd think there was Abrams tank over the ceiling. The difference is not in the cost of the A/C system, it is a factor of how the installation was done. There are techniques and products that will isolate the noise and vibration and installation details that do not use these will be very hard / impossible to retrofit.
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Installation details matter more than cost!!!
